1. Technical Field
The present invention relates to an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus.
2. Related Art
Image forming apparatuses in an electrophotographic system generally have the below-described structure and are operated according to the below-described process.
The surface of an electrophotographic photoreceptor is electrified to a predetermined polarity and a predetermined electric potential by an electrifier, and the electrified electrophotographic photoreceptor surface is imagewise exposed to light so as to remove the electric charge selectively, thereby forming an electrostatic latent image. Thereafter, a toner is adhered to the electrostatic latent image by a developing unit, and the latent image is developed as a toner image. The toner image is transferred to an image-receiving medium via a transfer unit, and the image-receiving medium is discharged as an image formed product.
Electrophotographic photoreceptors have the advantage that a high-quality image is obtained at high-speed. In recent years, therefore, the use thereof has been increasing in the field of copying machines, laser beam printers and the like.
Electrophotographic photoreceptors using a conventional inorganic material, such as selenium, selenium-tellurium alloy, selenium-arsenic alloy, or cadmium sulfide (inorganic photoreceptors), are known as electrophotographic photoreceptors used in these image forming apparatuses. In recent years, electrophotographic photoreceptors using an organic photoconductive material (organic photoreceptors), which are inexpensive and advantageous in terms of productivity and disposability, have started becoming mainstream.
A corona electrifying system using a color discharger has been hitherto used as the electrifying system. In recent years, a contact electrifying system, which has advantages such as low ozone generation and low power, has been put into practice and come into widespread use. In the contact electrifying system, an electroconductive member is used as an electrifying member and is contacted with or moved close to the surface of a photoreceptor, and voltage is applied to the electrifying member to electrify the photoreceptor surface. Systems of applying voltage to the electrifying member include direct current systems of applying only a direct current voltage, and alternating current superimposed systems of applying an alternating current voltage superimposed on direct current voltage. The contact electrifying system is advantageous in terms of miniaturization of apparatuses and reduced generation of gases such as ozone.
As the transfer system, a system of transferring a toner image directly onto a paper sheet has been the mainstream. However, in recent years, a system of using an intermediate transfer medium for transferring a toner image has been actively used since the choice of papers on which the toner image is transferred has expanded.